Among the many requirements of a next generation wireless access system, one of the most important requirements corresponds to being capable of supporting a high data transmission rate demand. In order to do so, a wide range of technologies, such as MIMO (Multiple Input Multiple Output), CoMP (Cooperative Multiple Point transmission), relay, and so on, are being extensively researched.
In the related art wireless access system, a single carrier was generally considered even though the uplink bandwidth and the downlink bandwidth were set to be different from one another. For example, in a single carrier basis, a wireless communication system, wherein the number of carriers configuring the uplink and the downlink is respectively equal to 1, and wherein the uplink bandwidth and the downlink bandwidth are symmetrical to one another, was generally provided.
However, considering the fact that the frequency resources are in a saturated state, as a solution for ensuring wideband bandwidth in order to meet with the higher data transmission rate demand, CA (carrier aggregation) is being adopted, wherein CA refers to a concept of designing each of the scattered bands to be capable of meeting with the basic (or essential) requirement of operating an independent system and of grouping (or aggregating) multiple bands to a single system.
Herein, a carrier corresponding to a bandwidth unit available for independent management may be referred to as a CC (Component Carrier). In order to support the increasing transmission capacity, the recent 3GPP LTE-A or 802.16m is extending its bandwidth to 20 MHz or more. In this case, one or more component carriers are aggregated so as to support the wideband. For example, if one component carrier supports a bandwidth of 5 MHz, 10 MHz, or 20 MHz, a maximum of 5 component carriers may be grouped (or aggregated), so as to support a system bandwidth of up to 100 MHz.
In case of using the carrier aggregation technology, data may be simultaneously transceived (or transmitted and/or received) through multiple uplink/downlink component carriers. Therefore, the user equipment may be capable of monitoring and measuring all component carriers.